Multiple tumoricidal effector mechanisms induced by adriamycin.

The antitumor cytotoxic mechanisms of Adriamycin-elicited peritoneal exudate cells were investigated. Peritoneal exudate cells from mice collected 1 day after an i.p. injection of Adriamycin (10 mg/kg) displayed enhanced cytotoxicity against P815 (natural killer-insensitive, macrophage-sensitive) but not YAC-1 (natural killer-sensitive) tumor cell lines. These cells contained a sufficient concentration of the drug to be cytotoxic for P815 tumor cells in 18-hr chromium release assays. Freeze-thaw lysates of these peritoneal exudate cells were found to be as cytotoxic to P815 as their corresponding whole cells. The lytic activity of these lysates was removed by centrifugation at 100,000 X g, indicating the insolubility of the effector moiety. These cells were also shown to produce significant amounts of superoxide anion and H2O2 in response to phorbol myristate acetate. A catalase-inhibitable augmentation of the cytotoxicity of these cells against P815 was observed when phorbol myristate acetate was added to the assay. Neutrophils and not macrophages were likely responsible for this effect. Peritoneal lymphocytes from mice given injections of Adriamycin 5 to 7 days previously were cytotoxic to YAC-1 tumor cells in 4-hr assays. Finally, peritoneal macrophages harvested 5 to 7 days after Adriamycin administration were cytotoxic to P815 in the absence of detectable Adriamycin. The addition of phorbol myristate acetate inhibited the lysis of P815 by these cells.